Apparatus for filament coiling



June 20, 1939. R. B. THOMAS 2,163,565

' APPARATUS FOR FILAMENT COILING Filed Oct. 12, 1938 2 Sheets-Sheet 2 Rai /0'}? B. Thomas,

INVENTOR.

ATTORNEY.

Patented June 20, 1939 UNITED STATES PATENT OFFICE 2,163,565 APPARATUS FOR. FILAIVIENT COILING Application October 12, 1938, Serial No. 234,636

9 Claims.

The present invention relates to the coiling of wire, and particularly to the coiling of tungsten wire for use in lamp filaments and the like.

An object of the invention is to facilitate the coiling of such wire.

A further object is to permit the coiling of wire which is too brittle to be coiled by the older methods.

Still another object is to make possible a higher speed of coiling on automatic machinery than is possible by the older methods, and to secure a greater uniformity among the coils produced on such machinery.

Other objects are the provision of a current of air heated to a predetermined temperature and arranged to flow over the wire being coiled near the point of coiling.

Still other objects and advantages of the invention will be apparent from the following description, taken in connection with the accompanying drawings in which:

Figure 1 is in elevation, partly in section, of ap; paratus according to my invention; and

Figure 2 is an enlarged sectional view of a coil passing through the air discharge tube according to'my invention.

In Figure 1, air under a pressure which may conveniently be in the neighborhood of two to five pounds per square inch, enters the device through the pipe I which contains a valve 2 arranged to open electrical switch 3 when the pressure drops below a fixed limit, two pounds per square inch, for example. The air passes through the T-joint ll and enters the cylindrical heater 5 between the outer casing 6, and the bafiie 'l. The air then passes around the other baiiles 8, 9, I0, along the path shown by the arrows, and through a cylindrical hole H in a ceramic piece 4|, set along the axis of the heater unit. Inside this opening ll, is set an electrical heating coil l2, which may be a wire helix with turns widely spaced so as not to impede the progress of the air through the path H. For clearness, the coil is shown as a straight wire in Figure 1.

Instead of one such path I I, along the axis, several may be set around, and parallel to the heater axis, if desired, the openings at each end of the heater being connected to common Outlets or inlets. The air on emerging from the heating path, passes into the hot air discharge tube 46, shown at right angles to the axis of the heater 5.

The heater 5, shown partly in section, comprises a cylindrical casing 6, conveniently of metal, containing several cylindrical baffles l, 8, 9, i0, concentric with the casing. Alternate baifies, if desired, may be supported from opposite end-plates l3, M, of the casing 6, and may then be shorter than the inside length of the outer. cylinder by an amount suillcient to permit the air stream to pass around the end of the baflles. The baffles may, for example, be shorter than the inside of the casing by an amount equal to the spacing between baffles, or even less.

Lead-in wires l5, iii are brought through the end-plate M of the heating unit 5. The wires must, of course, be insulated to prevent short-circuiting. They may be brought through the T- joint 4 and out through the plug H in the end of that joint.

The air current through the tube II is, of course, heated by the absorption of heat from the wire coil l2. If the air pressure drops too low, the air will absorb less heat and the coil may overheat, possibly burning out. A switch 3 is, accordingly, connected in series with the coil and arranged to be responsive to the air pressure in the line. For example, when the pressure drops below a predetermined value, the spring l9, will force the piston 20 down, thus opening the elec-: trical contacts l8, 2|, shown schematically. It will generally be desirable to insulate the piston from the electrical line, for example, by the insulating block 22.

By causing the air to enter the heater in the outside annular space between the outer casing 6 and the baflle 1, heat losses are reduced. The air is at its lowest temperature when it enters, and the heat loss from it to the outer casing will thus be small. Moreover, heat will flow from the coil l2 toward the outside of the cylinder, and this heat will encounter and warm the air, as the latter passes around the baffles, so that the final heating as the air passes through the tube ll, containing the coil l2, will be more effective. The heating unit is thus very efiicient, which means that it can be made quite small, and thus readily adaptable to the present types of coiling machine for lamp filament wire.

For example, I have made a heater such as shown in the drawings, with an outer casing 6 of only two inches diameter and of only two and three-quarters inches in length, and with a heating coil using 150 to 200 watts and an air pressure of two to three pounds per square inch.

As shown more clearly in Figure 2, in modern coiling machines for tungsten wire, a mandrel 23, generally of a metal such as steel or molybdenum, is caused to move along its own longitudinal axis, that is in the direction of the arrow shown in Figure 2, by rotating the spool 24 to which an end or the mandrel is fixed. The wire 25 to be coiled passes between the bridge pin 26 and the sapphire die 21, in a manner well known to the art, the die being forced against the wire by the spring 29. The die and its spring are held in the spindle 28. A bobbin 30, free to rotate around the spindle 28, holds the wire to be wound, which runs over the pulleys 3|, 32, and onto the mandrel 23, between the bridge pin 26 and the die 21.

The pulleys 3|, 32, are attached to the spindle 28 by the piece 41, and revolve with it, around the mandrel 23, thus coiling the wire 25 around the mandrel. The point of coiling is the place where the wire 25 meets the mandrel 23.

A stream of hot air is'directed at the point of coiling from the direction toward which the mandrel moves, by the heated air discharge tube 46, shown in detail in Figure 2. The air enters the discharge tube at a point along the side of the latter and travels toward the open end 33 of the tube. The discharge tube is arranged with its axis concentric with that of the mandrel 23, which passes through the tube along the tube axis. The end 34 of the tube, farthest from the point of coiling preferably has an inside diameter large enough to pass the mandrel, with the coil wound upon it, but not large enough to allow the leakage of much air.

I have, for example, used a diameter of 0.025 inch for coiling 0.0017 inch diameter wire on a 0.0035 inch mandrel, and have maintained this diameter for a distance of about three-sixteenths of an inch from the end of the tube. The longer this small diameter path is made, the less the leakage of air out that end of the tube.

The end of the discharge tube facing the point of coiling has a uniform inside diameter, considerably larger than the inside diameter of the opposite end, from the point where the air enters the side of the tube to the point where it leaves the tube, except that the diameter may flare outward slightly at the very end of the tube. For example, in the discharge tube of the preceding paragraph the diameter may be one-sixteenth of an inch, and may flare outward to about one-eighth of an inch, in a distance of about three sixty-fourths of an inch from the end of the tube, as shown in Figure 2. This short flare at the end is for the purpose of facilitating the threading of the mandrel through the tube and onto the spool 24, before starting the winding apparatus. The flared portion should be made as short as possible, since the heated air expands when the diameter of the tube increases, thereby cooling the air.

It will be observed that the spool 24 revolves, slowly pulling the mandrel 23 through the spindle 28, die 21, and discharge tube 46. At the same time the revolving of the spindle 28, with its attached pulleys 3| and 32, revolves the tungsten wire 25, .whose free end had previously been attached to the mandrel, around the mandrel, thus forming a coil of wire around said mandrel. The sapphire die 21 and bridge pin 26 guide the wire into its proper place on the mandrel, the bridge pin rotating with the spindle in the bridge-pin holder 35.

The discharge tube 46 directs a stream of heated air on the wire to be coiled, and on its surroundings, at the point of coiling, that is at the point where the wire passes between the die 2'! and bridge-pin 26 and meets the mandrel around which it is to be coiled. The mandrel 23 with the wire 25 coiled around it then passes through the tube 46, still in the stream of heated air, and finally leaves the tube, through the small diameter end of the latter. The wire thus receives some slight measure of annealing after coiling, and

, moreover heat is conducted back along the wire and mandrel to aid in heating said wire and mandrel at the point of coiling.

In the particular discharge tube whose dimensions were occasionally noted in the foregoing paragraphs, the outside length of the discharge tube, along the axis of the wire mandrel, was fifty-four sixty-fourths of an inch. The mandrel speed was about 0.6 meter per minute, and the spindle revolved the tungsten wire around the mandrel at a speed of 8800 revolutions per minute. The mandrel was of steel and was 0.0035 inch in diameter. The wire wound on the mandrel was of tungsten 0.0017 inch diameter. The wire had been rejected as too brittle for coiling on our usual machine, operating at 5000 revolutions per minute, but coiled easily, with no breaks in the wire, on an identical machine using my heated air treatment as described in the present specification. The

wire coiled not only at 5000 revolutions per minute, but also at speeds as high as 8800 revolutions per minute. The heating coil l2 had an input of 150 to 200 watts, and the temperature of the air, measured with a thermocouple at the point of coiling, was 180 degrees centigrade.

After the tungsten wire had been wound and cut to the proper length of coil, the mandrel was removed by dissolving it in a solution of acid, such as 20% sulphuric and 80% nitric acid, which does not affect the tungsten. The coil then remained, free from the mandrel, and was mounted on leads projecting from a glass stem and sealed into a lamp bulb, which contained a filling of argon gas at a pressure of about 600 mm. of mercury. The lamp was found satisfactory in every way, and had a greater efllciency for its rated life than had lamps made similarly, but with wire which had been coiled without the heated air stream.

Referring again to Figure 1, it will be noted that metal end plates l3 and I4, are attached to the ends of the cylindrical casing 6, and that the bottom plate has a flange 48, through which it is screwed to the top of the table 36 holding the winding apparatus.

The fiange has a greater depth than the remainder of the end plate and spaces the remainder of the plate from the table-top 36, an amount sufiicient for air to flow out of a hole in the tabletop and through a multiplicity of openings in the end plate l4, one of which openings is shown in the drawings, into the heating unit 5, between the outer casing 6, and baille I. The T-joint is attached to the hole in the bottom of the tabletop, to supply it with air.

The air discharge tube 46, in order to direct air on the point of coiling of the wire, has to project inside the bridge-pin holder which rotates, with the spindle, at speeds often as high as 8800 R. P. M.; and the mandrel plus its coiled wire passes through an opening of small diameter at the end of tube ll, farthest from the point of coiling. The tube H, must, accordingly, be fixed quite accurately in position. It must, in addition, be readily removable, because access to the spindle, bridge pin, and die is often necessary. The discharge tube was consequently made in a T-shape, with the vertical leg 31 of the T sliding part way into a vertical tube 38, at the top of the heater unit, with a tapped projection 39 on the leg 31, above the tube 38. This projection 39 fits into an arm 40 projecting from the supports for the spindle and a set screw 42, having an insulating knob 43, fits through the end of 2,1cs,sos

the arm 40, and screws into the projection 39 on the tube 31. The arm 40 is insulated from a heater tube 31 between the insulating block H. A set screw 42 has a tapered portion 45, which fits into a coresponding portion of the opening in the arm 40. The tube may then be readily removed and re-inserted, the set screw fixing it in alignment.

By my invention I have succeeded in coiling at a speed as high as 8800 R. P. M., tungsten wire which was too brittle to be coiled by the usual methods even at speeds as low as 2500 R. P. M.

While particular embodiments of my invention have been described for convenience, in this specification, the broad aspects of the invention are not to be considered as limited thereby in any way.

What I claim is:

1. In combination, means for moving a mandrel in the direction ofthe longitudinal axis of said mandrel, means for coiling a wire around the periphery of said mandrel, and a tube concentrio, with the axis of the mandrel and arranged to direct a stream of heated air around the mandrel and its coiled wire at the point of coiling.

2. The combination of claim 1 in which-=the concentric tube has an inlet for'a current of heated air at a point between its ends, and in which the interior of the tube nearest the point of coiling is large enough to direct a current of heated air over the wire being coiled at the point of coiling, and in which the other end of the tube is of a diameter just large enough to provide sufllcient clearance for the mandrel and coiled wire,

without allowing the escape of appreciable air. 3. In combination, means for moving a mandrel along its longitudinal axis, means for coiling a wire around the periphery of said mandred, a tube concentric with the direction of motion of 40 the mandrel and having an inlet for air, means for directing a current of air to said inlet, and means for heating said current of air before it reaches said inlet.

4. In combination, means for moving a mandrel along its longitudinal axis, means for coiling a said tube nearest the point of coiling being open to direct air against the wire at said point of coiling, the end of said tube farthest from the point of coiling having a diameter just large enough to allow the mandrel bearing the coiled wire to pass through with clearance, means for directing a current of air to the inlet of said tube, and means for heating said current of air before it reaches said inlet.

5. In combination, means for moving a mandrel in the direction of the longitudinal axis of said mandrel, means for coiling a wire around the periphery of said mandrel, and a tube concentric with the axis of the mandrel and arranged to direct a stream of heated gas around the mandrel and its coiled wire at the point of coiling.

6. The combination of claim 5, in which the concentric tube has an inlet for a stream of heated gas at a point between its ends, and in which the interior of the tube nearest the point of coiling is large enough to direct a stream of heated gas over the wire being coiled at the point of coiling, and in which the other end of the tube is of a diameter just large enough to provide sufficient clearance for the mandrel and coiled wire, without allowing the escape of appreciable gas.

'7. In combination, means for moving a mandrel along its longitudinal axis, means for coiling a wire around the periphery of said mandrel, a tube concentric with the direction of motion of the mandrel and having an inlet for gas, means for directing a current of gas to said inlet, and means for heating said current of gas before it reaches said inlet.

8. In combination, means for moving a mandrel along its longitudinal axis, means for coiling a wire around the periphery of said mandrel, a tube arranged so that the mandrel passes through it after the point of coiling, said tube having an inlet for gas at a point along its side, the end of said tube nearest the point of coiling being open to direct gas against the wire at said point of coiling, the end of said tube farthest from the point of coiling having a diameter just large enough to allow the mandrel bearing the coiled wire to pass through with clearance, means for directing a current of gas to the inlet of said tube. and means for heating said current of gas before it reaches said inlet.

9. In combination, means for forming a wire into a coil, and a tube concentric with the axis of the formed coil and arranged to direct a stream of heated gas around the coiled wire at the point where the wire is formed into a coil.

RALPH B. THOMAS. 

